Anticholinergic suppression of ovine fetal swallowing activity

Nijland, Mark J.; Chao, Conrad R.; Ross, Michael G.

doi:10.1016/s0002-9378(97)70024-3

Cited by 17 publications

(14 citation statements)

References 19 publications

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“…Hence, it is unlikely that propranolol has any central effects relevant to this study, but these cannot be excluded for atropine. Atropine administration may cause subsequent changes in the CNS in terms of changed ECoG sleep states (21) or nearly exclusive high-voltage ECoG sleep state (1). This may influence the CNS generators of vagal activity and, thus, the vagal influences on fHRV.…”

Section: Discussionmentioning

confidence: 99%

Nonlinear properties of vagal and sympathetic modulations of heart rate variability in ovine fetus near term

Frasch¹,

Müller²,

Hoyer³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Frasch MG, Mü ller T, Hoyer D, Weiss C, Schubert H, Schwab M. Nonlinear properties of vagal and sympathetic modulations of heart rate variability in ovine fetus near term. Am J Physiol Regul Integr Comp Physiol 296: R702-R707, 2009. First published December 17, 2008; doi:10.1152/ajpregu.90474.2008.-Fetal heart rate (FHR) monitoring is commonly used although clinical studies questioned its diagnostic value. Sophisticated FHR variability (fHRV) measures such as fHRV complexity may improve the sensitivity and specificity of FHR monitoring. A more detailed understanding of the physiology underlying fHRV complexity is essential to harness its use for monitoring fetal health. To examine the specific effects of vagal and sympathetic modulations on fHRV complexity, we blocked vagal activity with atropine and sympathetic activity with propranolol in near-term fetal sheep (n ϭ 7, 0.85 gestation). Under these conditions, we analyzed the linear and nonlinear parts of fHRV complexity from autonomic information flow. Overall fHRV complexity decreased with both drugs compared with nonrapid eye movement sleep baseline (P Ͻ 0.05). With atropine, this was because of a decrease of the linear part of fHRV complexity on the long-term time scale (P Ͻ 0.05), suggesting that vagal modulation of fHRV is adequately described by linear fHRV measures. With propranolol, the nonlinear part of fHRV complexity decreased on the short-term time scale (P Ͻ 0.05), suggesting that sympathetic influences on fHRV can be detected by the nonlinear part of fHRV complexity. Thus the complex interplay of vagal and sympathetic modulations of fHRV is reflected differently and specifically in the linear and nonlinear properties of fHRV complexity, and on different time scales. Analysis of linear and nonlinear properties of fHRV may improve sensitivity and specificity of FHR monitoring. fetal sheep; autonomic nervous system; autonomic information flow; complexity FETAL HEART RATE (FHR) monitoring is used to monitor fetal well-being noninvasively in utero. Some studies questioned its diagnostic value (24). Recent studies in human fetuses suggested potential of FHR variability (fHRV) complexity estimation to improve clinical monitoring of fetal health (18,31). This requires a deeper understanding of the physiological meaning of fHRV complexity, including how its linear and nonlinear properties are modulated by sympathetic and vagal activity of the autonomic nervous system (ANS). Understanding fHRV dynamics during physiological (e.g., sleep states dependent changes) and pathophysiological (e.g., asphyxia) conditions has evolved over the past two decades, propelled by analyses of the linear aspects of fHRV in human and ovine fetuses (4,11,16,20,29,32). However, characterization of the linear fHRV properties is fundamentally limited in its power to describe the nonlinear structure of the underlying sympathovagal interactions (12,14).The origin of the nonlinearity of sympathovagal interactions lies in their intrinsic complexity. This complexity emerges from intera...

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Section: Discussionmentioning

confidence: 99%

Nonlinear properties of vagal and sympathetic modulations of heart rate variability in ovine fetus near term

Frasch¹,

Müller²,

Hoyer³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Central injection of atropine in rats, a cholinergic muscarinic receptor antagonist, completely inhibits carbachol-induced drinking (9,22). In fetuses, a previous study has shown that cholinergic effects on fetal swallowing activity by using intravenous injection of cholinergic antagonist atropine sulfate in sheep (28). To our knowledge, the present study was the first to examine the fetal swallowing and renal responses in response to direct central cholinergic stimulation signals in utero.…”

Section: Discussionmentioning

confidence: 60%

“…Previous studies also have demonstrated that fetal swallowing activity occurred in association with electrocortical activity and that alterations in fetal electrocortical activity may affect fetal swallowing by using intravenous injection of cholinergic antagonist atropine sulfate passing the blood-brain barrier vs. atropine methyl nitrate acting peripherally only in fetal sheep (28). Because fetal swallowing occurs predominantly during LV ECoG periods (14), change of the relative duration of LV periods may influence the swallowing rate.…”

Section: Discussionmentioning

confidence: 99%

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Central cholinergic mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term

Shi

Mao²,

Zeng³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term. Am J Physiol Regul Integr Comp Physiol 296: R318 -R325, 2009. First published September 10, 2008 doi:10.1152/ajpregu.90632.2008.-Fetal swallowing and renal metabolism contribute importantly to amniotic and body fluid homeostasis. To determine central cholinergic modulation of swallowing activity and renal excretion associated with neural activity, we examined the effects of intracerebroventricular injection of carbachol, a cholinergic agonist, in ovine fetuses at 0.9 gestation. Fetuses were chronically prepared with thyrohyoid, nuchal and thoracic esophagus, and diaphragm electromyogram electrodes, as well as lateral ventricle and vascular catheters. Electrodes were also implanted on the parietal dura for determination of fetal electrocorticogram (ECoG). After 5 days of recovery, fetal swallowing, ECoG, and urine output were monitored during basal period and the experimental period following intracerebroventricular injection of 0.9% NaCl as the control (n ϭ 5) or carbachol (3 g/kg, n ϭ 5). Central carbachol did not significantly change fetal low voltage (LV) and high voltage (HV) ECoG temporal distributions. However, swallowing activity during LV ECoG was elevated significantly after intracerebroventricular carbachol. Associated with the swallowing activation, c-fos immunoreactivity in the putative dipsogenic center, subfornical organ, was enhanced significantly. The fetal urine flow rate and renal Na ϩ , K ϩ , and Cl Ϫ excretion were markedly increased following intracerebroventricular carbachol and sustained at the high level for at least 2 h. The results indicate that the central cholinergic mechanism is established and functional in regulation of fetal behavior and renal excretion at least at 0.9 gestation, which plays an important role in maintenance of fetal body fluid homeostasis.fetus; carbachol; thirst STIMULATED WATER INTAKE, IN concert with renal water and electrolyte excretion, is the fundamental physiological mechanism that maintains body fluid homeostasis. It is well established that in adult animals, central cholinergic mechanisms play an important role in the control of cardiovascular and body fluid homeostasis (12,15). Central application of cholinergic agonist, carbachol, elicits a variety of physiological responses, including natriuetic, dipsogenic, and pressor responses, as well as vasopressin secretion (2,23,44). Our recent studies demonstrated that intracerebroventricular injection of carbachol also produced pressor responses (42) in the ovine fetus near term, indicating that the central cholinergic mechanism-mediated cardiovascular regulation is functional before birth. However, the role of central cholinergic mechanisms in fetal fluid balance and renal excretion is largely unknown.Progress has been made in demonstrating that swallowing activity can be regulated by hyperosmotic, hypovolemic, and other stimuli such as ANG II and neuropeptide Y in late gestation (31,33,48,49). Fetal renal flu...

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“…Nearterm ovine fetal swallowing activity occurs predominantly during low-voltage electrocortical activation. Atropine suppressed fetal swallowing activity in the ovine fetus (56), while carbachol increased high-voltage fetal sheep electrocortical activity and breathe amplitude. These effects were mediated by M 1 receptors (57).…”

Section: First Trimestermentioning

confidence: 88%

Development of fetal nicotine and muscarinic receptors in utero

Mao¹,

Lv²,

et al. 2007

Braz J Med Biol Res

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The role of acetylcholine in the central and peripheral nervous systems is well established in adults. Cholinergic modulation of vascular functions and body fluid balance has been extensively studied. In the embryo-fetus, cholinergic receptors are widespread in the peripheral and central systems, including smooth muscle and the epithelial lining of the cardiovascular, digestive, and urinary systems, as well as in the brain. Fetal nicotine and muscarinic receptors develop in a pattern (e.g., amount and distribution) related to gestational periods. Cholinergic mechanisms have been found to be relatively intact and functional in the control of vascular homeostasis during fetal life in utero at least during the last third of gestation. This review focuses on the development of fetal nicotine and muscarinic receptors, and provides information indicating that central cholinergic systems are well developed in the control of fetal blood pressure and body fluid balance before birth. Therefore, the development of cholinergic systems in utero plays an important role in fetal vascular regulation, gastrointestinal motility, and urinary control.

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Anticholinergic suppression of ovine fetal swallowing activity

Cited by 17 publications

References 19 publications

Nonlinear properties of vagal and sympathetic modulations of heart rate variability in ovine fetus near term

Nonlinear properties of vagal and sympathetic modulations of heart rate variability in ovine fetus near term

Central cholinergic mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term

Development of fetal nicotine and muscarinic receptors in utero

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